1. Field of the Invention
The present invention relates to a steering control technology.
2. Description of the Prior Art
In general, a steering apparatus of a vehicle is an apparatus for changing the direction along which a vehicle moves according to a driver's intention, and is an apparatus for helping a driver to move the vehicle in a direction desired by a driver by arbitrarily changing a rotation center about which the front wheel or wheels of the vehicle turn.
On the other hand, when the driver operates a steering wheel (steering gear) of the vehicle, the steering control apparatus assists the driver's steering wheel operating forces by using a steering motor so that the driver can easily change the direction along which the vehicle moves by using a small force.
The steering control apparatus described above is largely divided into a hydraulic steering control apparatus and an electronic steering control apparatus.
In the hydraulic steering control apparatus, when a hydraulic pump connected to a rotating shaft of an engine supplies a hydraulic fluid to a working cylinder connected to a rack bar, the piston of the working cylinder supplied with the hydraulic oil moves so as to assist the steering wheel operating forces, thereby allowing the driver to perform a steering operation with a small force.
On the other hand, since the electronic steering control apparatus includes a steering motor and an Electronic Control Unit (ECU) provided in a rack bar or a column instead of the hydraulic pump and working cylinder, the motor power can assist the operating force.
More specifically, the electronic steering control apparatus applies, to the steering motor, an assist current generated based on a steering torque generated by the steering wheel (steering gear) operated by the driver, so as to assist the steering operation force.
However, in an actual operation of the electronic steering control apparatus, an assist current is generated due to the steering torque (disturbance) generated in an external environment as well as the steering torque generated by the steering wheel (steering gear), then the assist current is applied to the steering motor.
Therefore, there is a problem in that unnecessary vibration may occur in the steering wheel (steering gear) due to the disturbance in the external environment.